Why does my sister care about more about her friends than she does for me?

Whenever I try to hang out with her, she just distances herself. She never talks to me at home and acts like I don’t exist. She’s always starting fights with me even though I haven’t done anything and she’s always passive aggressive around me. Whenever I try to talk about if I feel down (I have depression) she dismisses it but when her friends call her in their time of need she’s there for them 😞her friends always mention how mean she is to me as well as my mother too. What can I do?
Why does my sister care about more about her friends than she does for me?
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